Various devices are known which utilize heat from the circulating engine coolant of a vehicle in order to raise the temperature of a supply of washer fluid. For example, U.S. Pat. No. 4,862,951, dated Sep. 5, 1989, discloses a windshield washer fluid heating apparatus which includes a cylindrical heater-exchanger housing that, via hose connectors, can be disposed into the coolant line between the engine and radiator, with the interior of the housing, through which the coolant flows, containing a tube coil that is helically wound in the longitudinal direction of the housing. The liquid which is to be heated flows through the tube coil. Similarly, U.S. Pat. No. 4,895,203 discloses a heat exchanger which utilizes waste heat from a motor vehicle engine cooling system to heat a source of water for use with showers and the like in a recreational environment.
Additionally, U.S. Pat. No. 4,354,548 discloses a heat exchanger for automobile washer systems which utilizes a central flow through heat exchanger having a body with approximately the same diameter as the return hose extending between a car engine and its cooling system. Again this device employs the use of conduits wound around one another to accomplish heat exchange. Each of these prior art devices relies upon the use of helically wound heat exchange tubes, and although this configuration provides a large surface area along which heat exchange may occur, the manufacturing costs associated with helical winding may prove prohibitive in most applications.
In U.S. Pat. No. 3,632,042 a windshield cleaning system is disclosed which uses heated engine coolant fluid flowing constantly through a circuit from the heater hose, through a conduit, passing through the windshield washer fluid reservoir in a W-shaped configuration, and then throughout the feed lines to the washer fluid spray nozzles. Although this invention incidently incorporates heat exchange by means of a flow through jacket along the windshield washer supply line, the initial source of fluid heating occurs by means of a bent tube heat exchange device located in the washer fluid reservoir. The costs associated with manufacturing the various system-components are high, and extensive modifications, including the addition of a specialized hot washer fluid pump, make wide-scale retrofitting of this system into existing vehicles impractical.
It is an object of the present invention to provide a washer fluid heater which will function effectively, yet does not require the use of a helical configuration of heat exchange components, since the use of such a helical component significantly increases manufacturing costs.
It is a further object of the present invention to provide a washer fluid heater which is simple and cost effective to assemble from known prefabricated components, and which does not require significant modification of the existing washer fluid supply systems which come as standard equipment on most automobiles.
It is a further object of the present invention to provide washer fluid heater which, through selection of materials and chamber volumes, has a short recovery time, such that even in the repeated use of washer fluid, a further fluid supply is heated for re-use within a short time lapse from the previous activation of the washer fluid spray nozzle.
It is yet a further object of the present invention to provide a washer fluid heater which will withstand the fluid pressure of heated washer fluid without leakage and without stress fractures in the various components due to differential expansion and contraction thereof.